Materials which may, via suitable temperature excursions, be reversibly switched between two structural phases characterized by different resistivities, have the potential to be employed as phase change memory materials. One such class of materials is a material that includes germanium (Ge) and antimony (Sb). Hereinafter the materials including Ge and Sb are referred to as GeSb materials.
In order to fabricate practical memory devices, it will be necessary to deposit the GeSb materials upon substrates of substantial topography complexity. A possible structure for implementing a phase change memory device is a line-and-via structure similar to those found in interconnect wiring structures. In such structures, the phase change material in the narrow via opening would constitute the active element of the memory device.
While this class of designs is attractive, they require for their fabrication that high aspect ratio (e.g., height to width ratio) vias be filled with the active material. Since desirable aspect ratios for the vias will typically exceed 3:1, this presents a substantial challenge for physically based deposition methods such as sputtering. As such, alternative deposition processes for filling high aspect ratio openings are being sought.
One promising candidate method for deposition of such materials is chemical vapor deposition. In CVD, numerous organometallic precursors (such as carbonyls, alkyls, etc) with reasonable vapor pressure exist for a large number of candidate metals. The problem to be faced with conventional CVD methods is in performing the deposition at a sufficiently low temperature (less than about 400° C.) while being able to fill high aspect ratio openings of a substrate with a GeSb material.
To date, there is no known chemical vapor deposition (CVD) method for depositing GeSb materials onto a substrate at temperatures less than 400° C. More particularly, there is no known CVD method for depositing GeSb materials which has the ability to fill high aspect ratio openings at temperatures of less than 400° C. As such, there is a need for the development of a chemical vapor deposition method in which the deposition method has the ability to form a blanket GeSb material onto a substrate as well as to effectively fill high aspect ratio openings with a GeSb material.